The disclosure of Japanese Patent Application No. 2000-036381 filed on Feb. 15, 2000 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of the Invention
The invention relates to a structure of a closed secondary battery module.
2. Description of the Related Art
Closed type secondary batteries are widely used as power supplies of various appliances because batteries do not allow leakage of an electrolytic solution, even if they are tilted, and can be used in any placement posture, such as dry batteries. Also widely used are battery modules integrally formed by connecting a plurality of closed secondary batteries so as to meet the power requirements of various appliances.
Such a battery module has a structure in which an internal space of a closed container is divided into a plurality of small cells. Each cell contains an electrolytic solution, a positive electrode plate, and the like. Each cell forms a small secondary battery. The cells are electrically connected in series or parallel. The battery module is provided with a positive terminal and a negative terminal for extracting power.
In some cases, a typical secondary battery experiences a battery internal pressure increase due to generation of a gas at an electrode plate depending on the condition of use or the charging/discharging condition of the battery. Furthermore, in other cases, the closed container receives external force due to, for example, some interference with the battery module. Taking such cases into consideration, an outer wall of the battery module is provided with such a strength that the outer wall will not easily break despite such a load.
However, if the internal pressure of the battery module rises above the withstanding pressure of the closed container, or if the battery module receives a great external force that exceeds an allowable value, there is a danger of formation of a crack or the like in an outer wall of the closed battery container.
Accordingly, it is an object of the invention to provide a closed battery module capable of avoiding formation of a crack in an outer wall of a closed container of the battery module even if the container receives a load that is greater than an allowable value.
To achieve the aforementioned and other objects, the closed battery module of the invention includes a partition dividing an internal space of a closed container into a plurality of cells, a unit cell formed in each of the cells divided by the partition, and a deformable portion provided in the partition. The deformable portion deforms before a stress greater than a predetermined allowable value occurs in an outer wall of the container by a load applied to the container.
Therefore, the stress occurring in outer walls of the container decreases. Hence, it is possible to avoid occurrence of stress greater than the predetermined allowable value.
The stress greater than the predetermined allowable value may be a stress that does not immediately form a crack in an outer wall but that forms a crack when applied repeatedly. If the stress occurring in the outer walls can be controlled to or below the allowable value, it is possible to prevent cracks or the like that might otherwise be formed in the outer walls.